Shortcomings of the isolated abyssal reservoir model for deglacial radiocarbon changes in the mid-depth Indo-Pacific Ocean

Abstract

Severely negative 14 C anomalies from the mid-depth Pacific and the Arabian Sea have been taken as support for the hypothesized deglacial release of a previously isolated, extremely 14 C-deplete deep ocean carbon reservoir. We report box model simulations that cast doubt on both the existence of the hypothesized deep reservoir and its ability to explain the mid-depth 14 C anomalies. First, the degree of ice age isolation needed to substantially reduce the deep 14 C of the deep reservoir causes anoxia and the trapping of alkalinity from CaCO 3 dissolution, the latter increasing atmospheric CO 2. Second, even with a completely 14 C-free deep reservoir, achieving the mid-depth 14 C anomalies of observed duration requires ad hoc stifling of aspects of deep circulation to prevent rapid dissipation of the anomalous 14 C-free carbon to the rest of the ocean and the atmosphere. We suggest that the mid-depth anomalies do not record basin-scale 14 C changes but are instead local phenomena. Copyright © 2011 by the American Geophysical Union.